21 May 2015

AT-3004D (CIS-12): MPSK 12-tones PSK-2, PSK-4 120 Baud

CIS-12 is a Soviet military pseudo OFDM 12-tones + 1 pilot tone modem allowing scrambled voice or data-communication at 120 Baud rate, modulation PSK-2 or PSK-4. CIS-12 is also known as MS5 or FIRE while the modem name is AT-3004D (or its newer counterpart AT-3104).

"An
interesting feature of these signals is that the sub-carriers are not
orthogonal, since the manipulation speed is 120 Hz and channel spacing
is 200: it means that each channel is formed separately, not as in OFDM
using IFFT all at once, although the OFDM technology is used. CIS-12
modems may appear in three different variants, according to the n-ary
PSK modulation: 2-PSK, 4-PSK offset (doesn't turn on 180^) and 4-PSK.Channels
1-10 are for user-data while 11 and 12 for the inspection. Accordingly,
the aggregate information rate is 1200 and 2400 (PSK-2 and PSK-4)."

PSK-2 waveform:

PSK-4waveform:KarapuZ sent me a sample of this mode along with his comment:

"this mode modem is less resistant to interference, it is mainly used to
transmit a surface wave, or at a distance of not more than one hop. A
chance to hear him in Italy is very small".